/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.accumulo.core.iterators;

/**
 * This callback handles the state of yielding within an iterator
 */
public class YieldCallback<K> {
  private K key;

  /**
   * Called by the iterator when a next or seek call yields control.
   *
   * @param key
   *          the key position at which the iterator yielded.
   */
  public void yield(K key) {
    this.key = key;
  }

  /**
   * Called by the client to see if the iterator yielded
   *
   * @return true if iterator yielded control
   */
  public boolean hasYielded() {
    return (this.key != null);
  }

  /**
   * Called by the client to get the yield position used as the start key (non-inclusive) of the
   * range in a subsequent seek call when the iterator is rebuilt. This will also reset the state
   * returned by hasYielded.
   *
   * @return <code>K</code> The key position
   */
  public K getPositionAndReset() {
    try {
      return this.key;
    } finally {
      this.key = null;
    }
  }
}
